CRYSTAL GROWTH OF CaWO4 AND Nd2(CO3)3.8H2O BY THE GEL TECHNIQUE.
Abstract
Spherulites (up to 2 mm in diameter) and single crystals of CaWO4 have been synthesized by reacting CaCl2 and Na2WO4 within acetic acid-Na2SiO3.9H2O gels. High calcium concentrations favored the growth of clear spherulites, whereas high tungstate concentrations resulted in opaque spherulites. The addition of NH4Cl to the gel system lead to the formation of single crystal needles of CaWO4. Lavender-colored rhombic plates, dendrites, and spherulites of Nd2(CO3)3.8H2O were synthesized for the first time in a gel. Utilizing low pH HCl-Na2SiO3.9H2O gels, the crystals formed by recrystallization from an initial precipitate (perhaps Nd2(CO3)3.Na1CO3.nH2O) or at gel-gel and gel-bubble interfaces. Differential thermal analysis on the material showed that six waters of hydration are lost beginning at 77 C and the last two beginning at 121 C; infrared and visible absorption spectra were also obtained. In transmitted light microscopy all the crystals exhibited a highly symmetric domain structure and a resulting strain birefringence. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1970
- Accession Number
- AD0710236
Entities
People
- Henry M. Gehrhardt
- James W. McCauley
Organizations
- United States Army Research Laboratory